Project Year 2015

Better control of bacteria

New packaging methods that inhibit bacteria maintain the quality of salmon fillets longer.

Hygiene, cleaning and storage conditions are decisive factors that affect product quality. Additionally, the choice of packaging method is important for shelf life. Requirements to packaging and storage will vary, and must also be tailored to different fish species and products.

The goal of this research project has been gain control of the raw material quality of pre-rigor filleted salmon. The first step was to identify which bacteria contribute to reducing quality and shelf life.

So far, the major part of the fish delivered from fish farmers to processing in Norway or abroad has been whole fish – this is because there is a widespread perception that the quality of whole fish is better than that of filleted fish. However, trials show that the bacteria content is approximately the same for pre-rigor filleted salmon as for whole fish after nine days of storage at 2°C. Nevertheless, it cannot be concluded that filleted fish in general is of the same quality as whole fish as several aspects are affecting the quality.

Based on the knowledge of which bacteria exist and dominate in various stages of production, on both raw material and product, Nofima’s researchers have investigated different packaging methods for different products.

The removal of oxygen can reduce the growth of bacteria that require oxygen to grow. Vacuum packaging accomplishes this. On the other hand, the growth of some bacteria are inhibited when CO2 is present. The use of CO2 therefore leads to reduced growth of some spoilage bacteria.

It is possible to achieve a 20 day of microbiological shelf life for fillet packed with CO2 and stored at 2°C.

“We have also studied at the requirement to oxygen barrier in the packaging material for different products and packaging methods. The use of plastic material with a good oxygen barrier can have a positive effect on product quality. The better the barrier, the less oxygen and the fewer bacteria”, explains senior researcher Marit K. Pettersen.